______________2.1.  ___111

           
 ( 10 /  )        
      .

        
  .      -
,     ,   
.  ,     (KB,   ), 
    (Amplitude Modulation, AM)  
     ,   , 
    .    ,
     (),   
  (Frequency Modulation, FM),    -
  (  microwaves).    ( 4 )   
         
    .    -
   ,   ,    -
.

        
   ,     -
-.        -
 ,       . 
    ,    -
   ,    .    
        100  
.         
,       ,  
          -
 ,    , ,  ,  . .

2.1.2.   

   ("  DCE  Data Circuit terminating Equipment)
        -
   ,  ,  . 
       .  DCE
 ,    ISDN,  , -
    .  DCE   
,            -
 .

   ,    
         ,
      (  DTE  Data
Terminal Equipment).  DTE     -
  .        .

    DCE  DTE    
 . ,       -
 ,   DTE,      , 
 DCE.